I've always been curious as to how it could possible take so long to update the programming.

Are they using a 20 year old RS232-A serial interface at 300 baud? Do some motors or elecrical items have to physically cycle through moverments or something? is some of the memory really slow/large flash memory?

Does anyone know why it takes so long to update the programming?

Hopefully the day will come when people can update the programming themselves. The Micrsoft/Ford Sync voice control system for phone/media is perhaps a first step, as you can download updates from the internet onto a flash drive, plug the flash drive into the usb port in the car, and the system will update itself using the file on the flash drive.